Wafer stepper method utilizing a multi-segment global alignment mark

Abstract

A multi-segment alignment mark useful for a variety of processes is described. The multi-segment alignment mark comprises a plurality of segments wherein each of the segments comprises a series of sub-segments wherein each of the sub-segments comprises a series of spaces and lines, each sub-segment having the same width but having a different number of spaces and lines within the width depending on the relative width of the spaces and lines. A wafer stepper detects signals from each of the sub-segments and uses the best signal to achieve alignment.

What is claimed is: 
     
       1. A method of using a wafer stepper to align a reticle comprising: using a multi-segment alignment mark comprising a plurality of segments wherein each of said segments comprises a series of sub-segments wherein each of said sub-segments comprises a series of spaces and lines each sub-segment having the same width but having a different number of spaces and lines within said width depending on the relative width of said spaces and lines wherein said wafer stepper detects a signal from each of said sub-segments and uses the best said signal to align said reticle.   
     
     
       2. The method according to claim 1 wherein said wafer stepper detects said sub-segments of said multi-segment alignment mark by light interference. 
     
     
       3. The method according to claim 1 wherein said wafer stepper detects said sub-segments of said multi-segment alignment mark by bright field contrast. 
     
     
       4. The method according to claim 1 wherein said wafer stepper detects said sub-segments of said multi-segment alignment mark by dark field polarization effect. 
     
     
       5. The multi-segment alignment mark according to claim 1 wherein each of said segments has an identical series of sub-segments. 
     
     
       6. The multi-segment alignment mark according to claim 1 wherein each of said segments has a different series of sub-segments. 
     
     
       7. The multi-segment alignment mark according to claim 1 wherein each of said lines comprises chrome. 
     
     
       8. The method according to claim 1 wherein said multi-segment alignment mark is formed on a scribe line. 
     
     
       9. The method according to claim 1 wherein two consecutive uses of said wafer stepper to align said reticle may use two different said sub-segments.